TSH (Thyroid Stimulating Hormone)
| Clinical | Optimal | |
|---|---|---|
| Male | 0.27 - 4.2 mIU/L | 0.4-4.0 mIU/L (optimal 0.5-2.5 mIU/L) |
| Female | 0.27 - 4.2 mIU/L | 0.4-4.0 mIU/L (optimal 0.5-2.5 mIU/L) |
What is TSH (Thyroid Stimulating Hormone)?
Thyroid stimulating hormone (TSH) is produced by the pituitary gland at the base of your brain. Its role is to control and regulate the thyroid gland, a butterfly-shaped organ in your neck that produces thyroid hormones (T3 and T4). TSH acts as a thermostat: when thyroid hormone levels drop, the pituitary releases more TSH to stimulate the thyroid; when thyroid hormones are adequate, TSH decreases.
This feedback mechanism means that TSH levels move in the opposite direction to thyroid hormone levels. A high TSH typically indicates an underactive thyroid (hypothyroidism), as the pituitary is working harder to stimulate an underperforming thyroid. Conversely, a low TSH suggests an overactive thyroid (hyperthyroidism), where excess thyroid hormones are suppressing TSH production.
TSH is the most sensitive first-line screening test for thyroid disorders in the UK and is the starting point for any thyroid assessment. Omniwo measures TSH alongside Free T4 and Free T3 to give you a complete picture of your thyroid function.
Why TSH (Thyroid Stimulating Hormone) Matters for Your Health
Your thyroid gland controls the metabolic rate of virtually every cell in your body. Thyroid hormones influence energy production, body temperature, heart rate, brain function, digestion, bone health, and mood. Even subtle thyroid dysfunction can have wide-ranging effects on your quality of life and long-term health.
Thyroid disorders are remarkably common in the UK, affecting approximately 1 in 20 people. They are more prevalent in women and increase with age. Many cases remain undiagnosed because symptoms develop gradually and can be attributed to other causes such as stress, ageing, or lifestyle factors.
For longevity, optimal thyroid function is essential. Hypothyroidism accelerates cardiovascular risk through elevated cholesterol and blood pressure. Subclinical thyroid dysfunction, where TSH is abnormal but thyroid hormones remain in range, has been linked to increased cardiovascular risk, cognitive decline, and reduced quality of life, making proactive testing valuable.
TSH (Thyroid Stimulating Hormone)& Your Wearable Data
Thyroid-stimulating hormone (TSH) is the primary screening marker for thyroid dysfunction. While wearables cannot measure TSH, they can detect patterns associated with thyroid disorders. Hypothyroidism (high TSH) often manifests as unexplained elevated resting heart rate at rest or, conversely, bradycardia, reduced exercise capacity, and declining VO2 max despite consistent training — all detectable through wearable data.
Sleep patterns tracked by your wearable are affected by thyroid status. Hypothyroidism is associated with excessive sleep need, poor sleep quality, and daytime fatigue, while hyperthyroidism (low TSH) can cause insomnia, restless sleep, and elevated nocturnal heart rate. Tracking these wearable metrics alongside TSH results helps monitor treatment effectiveness.
HRV data from your wearable provides additional thyroid-related insights. Hypothyroidism tends to reduce HRV, while hyperthyroidism may cause erratic HRV patterns with sympathetic dominance. Monitoring HRV trends during thyroid treatment can serve as a real-time indicator of whether medication is moving your physiology toward optimal function.
What High TSH (Thyroid Stimulating Hormone) May Suggest
Elevated TSH indicates that your pituitary gland is working harder than normal to stimulate the thyroid, which typically means the thyroid is underperforming. TSH between 4.0-10.0 mIU/L with normal Free T4 is termed subclinical hypothyroidism, while TSH above 10.0 mIU/L or TSH elevation with low Free T4 suggests overt hypothyroidism.
The most common cause of hypothyroidism in the UK is Hashimoto's thyroiditis, an autoimmune condition where the immune system gradually damages the thyroid gland. Other causes include iodine deficiency, previous thyroid surgery or radioactive iodine treatment, certain medications (including lithium and amiodarone), and pituitary disorders.
Symptoms of an underactive thyroid include fatigue, weight gain, cold intolerance, dry skin, constipation, brain fog, depression, hair thinning, and menstrual irregularities. These develop gradually, which is why many people do not realise their thyroid is underperforming until blood tests reveal the issue.
What Low TSH (Thyroid Stimulating Hormone) May Suggest
Low TSH indicates that the pituitary is being suppressed, usually because the thyroid is producing too much hormone (hyperthyroidism). TSH below 0.1 mIU/L is more likely to represent significant overactivity, while TSH between 0.1-0.4 mIU/L may indicate subclinical hyperthyroidism.
The most common cause of hyperthyroidism in the UK is Graves' disease, an autoimmune condition that stimulates the thyroid to overproduce hormones. Other causes include toxic nodular goitre, thyroiditis (where stored hormones leak from an inflamed thyroid), and excessive iodine intake.
Symptoms of an overactive thyroid include unexplained weight loss, rapid heartbeat, anxiety, tremor, heat intolerance, diarrhoea, excessive sweating, and difficulty sleeping. Hyperthyroidism can be serious if left untreated, particularly for cardiovascular health, and requires medical management.
How to Optimise Your TSH (Thyroid Stimulating Hormone)
Food
Ensure adequate iodine intake from sources such as fish, shellfish, seaweed, dairy, and iodised salt, as iodine deficiency impairs thyroid hormone production, Include selenium-rich foods such as Brazil nuts (2-3 per day), fish, and eggs, as selenium is essential for thyroid hormone conversion, Eat foods rich in zinc including pumpkin seeds, shellfish, and legumes, which support thyroid hormone synthesis, Avoid excessive consumption of raw cruciferous vegetables if thyroid function is borderline, as they contain goitrogens that may interfere with iodine uptake in large amounts
Lifestyle
Manage chronic stress, as prolonged cortisol elevation can suppress TSH and impair thyroid hormone conversion, Prioritise quality sleep, as sleep deprivation affects the hypothalamic-pituitary-thyroid axis, Reduce exposure to environmental endocrine disruptors found in some plastics, cosmetics, and pesticides, which may interfere with thyroid function, Exercise regularly but avoid overtraining, which can suppress thyroid function in susceptible individuals
Supplements
Selenium (100-200mcg daily, or 2-3 Brazil nuts) supports thyroid peroxidase enzyme function and T4 to T3 conversion, Zinc (15-30mg daily) supports TSH production and thyroid hormone synthesis, Vitamin D (1000-2000 IU daily if deficient) may support thyroid health, as vitamin D deficiency is associated with thyroid autoimmunity
When to Speak to Your GP
See your GP if your TSH results suggest levels above 4.0 mIU/L or below 0.4 mIU/L, as these may indicate thyroid dysfunction requiring further investigation with Free T4 and Free T3 testing. Seek prompt medical advice if TSH is significantly abnormal (above 10 or below 0.1 mIU/L) or if you are experiencing symptoms of thyroid dysfunction such as unexplained fatigue, weight changes, heart palpitations, or mood disturbances. Thyroid function should also be checked if you are planning pregnancy.
References
- NHS. Underactive thyroid (hypothyroidism) — Diagnosis. Updated 2024. nhs.uk
- NICE. Thyroid disease: assessment and management. NICE guideline NG145. nice.org.uk
- BMJ. Taylor PN, et al. Global epidemiology of hyperthyroidism and hypothyroidism. Nat Rev Endocrinol. 2018;14(5):301-316. pubmed.ncbi.nlm.nih.gov
- Lancet. Chaker L, et al. Hypothyroidism. Lancet. 2017;390(10101):1550-1562. pubmed.ncbi.nlm.nih.gov
- ATA. Jonklaas J, et al. Guidelines for the treatment of hypothyroidism. Thyroid. 2014;24(12):1670-1751. pubmed.ncbi.nlm.nih.gov
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.